The private sector parties included executives and directors of Siam Indica, a major rice trading company.
The two companies – Guangdong Stationery & Sporting Goods Import & Export Corp and Hainan Grain & Oil Industrial Trading Co – were given the rights to buy rice under the pledging scheme without having to face competition from other bidders, Mr Vicha said.
They then sold the paddy, which they bought at prices lower than the pledging price, to Thailand's domestic rice traders and to Siam Indica to resell, Mr Vicha said.
These practices caused serious damage to the country, he said.
The NACC has agreed that the actions of the 21 accused violated the Criminal Code, the law on state price biddingoffences and the National Anti-Corruption Act, Mr Vicha said.
The anti-graft body will forward the case to the Office of the Attorney-General to indict the 21 accused in court, Mr Vicha said.